Electromechanical timing device



United States Patent a 2,814,692 nLEcraoMEc-HANIcAL TIMING DEVICE Chris'tiaan J. Van Eyk, Byram, N. Y. Application November 22, 1954, Serial No. 470,393 Claims. (Cl. 200-90) This invention relates to electromechanical timing de vices, and particulary concerns an improved electromechanical timing device capable of maintaining a predetermined frequency of operation despite mechanical vibration and fluctuation of its supply voltage.

In this application the invention is shown as employed in a circuit for flashing the wing and tail lights of an airplane on and off at a predetermined frequency. in such an environment, a timing device may be subjected to extreme vibration for prolonged periods. Moreover, the operating voltage provided for the timing device by the aircraft electrical system may be poorly regulated and subject to considerable variation in accordance with such factors as the operating speed of the aircraft engines and varying load demands on the airplanes electrical source as various items of electrically powered equipment in the airplane go into and out of operation. Although the present invention is particularly well adapted to overcome the difiiculties of this particular application, it is by no means so limited in its utility, but, on the contrary, is equally well adapted for a wide variety of other uses.

In the drawings:

Figure 1 is a side elevational view, partly in section, of a timing device embodying features of the present in vention;

Figure 2 is an end elevational view of the device, looking toward the end which appears at the right in Figure l; and,

Figure 3 is a schematic diagram of an electrical wiring circuit incorporating the timing device of the present invention for the purpose of flashing the wing and tail lights of an airplane.

As may be seen in Figure l, the various elements of the timing device are mounted on a base plate 10. Near the left-hand end of this base plate, as viewed in Figure 1, is mounted a rotary solenoid 12, said solenoid being supported above the base by means of a bracket 14. The solenoid 12 includes a rotatable plate 16 secured at one end of a horizontal shaft 18 which extends through the body of the solenoid 12 and through the bracket 14 and projects a short distance beyond. The rotary solenoid 12 is of a commercially available type wherein energization of the solenoid causes the plate 16 to rotate rapidly in the direction indicated by the arrows A through an angle of approximately 67 degrees.

The plate 16 is normally maintained against a stop (not shown) by the action of a spiral return spring 20, the inner end of the return spring 20 being secured to the shaft 18 while its outer end is secured to a pin 21 projecting from the case of the solenoid 12. The solenoid 12 develops sufiicient power to rotate the plate 16 rapidly in the direction indicated against the resistance of the spring 26.

Projecting forwardly from the plate 16 is a pin 22 which engages the outer end of a spiral buffer spring 24, the inner end of which is secured at the left-hand end 2,814,692 Patented Nov. 26, 1957 of an oscillatory shaft 26. This shaft 26 is rotatably supported in ball bearings 28 carried by vertical plates 30 and 32 which project upwardly from the base plate 10.

The oscillatory shaft 26 has keyed to it a spur gear 34 which meshes with a pinion 36 of smaller diameter which is keyed to a countershaft 38 rotatably supported above the oscillatory shaft 26 in ball bearings 40 carried by the vertical plates 30 and 32. Also fixed on the countershaft 38 is a flywheel 42 having an appreciable mass which is principally concentrated near its periphery, and which is symmetrically disposed with respect to the axis of revolution of the countershaft so that the flywheel is substantially balanced both statically and dynamically.

At the right-hand end of the oscillatory shaft 26 beyond the vertical plate 32 is secured a switch-operating cam 44 which is adapted to cooperate with the actuating leaf 46a of an electrical switch 46 secured above the cam 44 ona bracket 48 which extends from the upper end of the adjacent vertical plate 32. In Figure 2 the cam 44 is shown in the position which it occupies when the timer is at rest, with the rotatable plate 16 of the solenoid 12 against the aforementioned step. In this position, it is out of engagement with the leaf 46a of the switch 46.

As may be seen in Figure 3, the switch 46 is a singlepole double-throw switch having a movable contact blade 46b, a normally closed fixed contact 46c, and a normally open fixed contact 46d. The contact blade 46b of the switch 46 is connected through a single-pole single-throw on-otf switch 5%) to one terminal of a source of electrical power 52, in this diagram schematically indicated as a battery. The other terminal of the source 52 is connected to one terminal of the winding of the solenoid 12, the other terminal of this winding being connected to the normally-closed fixed contact 460 of the switch 46. One set of incandescent electric lamps, indicated schematically at 54, is connected in parallel with the winding of the solenoid 12. Another set of electric lamps, indicated schematically at 56, is connected between the latter terminal of the power source and the normally open fixed contact 46d of the switch 46.

The operation of this mechanism is as follows: Closure of the on-ofi switch 50 (Figure 3) completes the circuit through the switch 46 and the winding of the solenoid 12. Thus the solenoid is energized and its movable plate 16 is rapidly rotated in a direction indicated by the arrow A in Figure 1 against the resistance of the spiral return spring 20. This motion, imparted through the pin 22 to the outer end of the spiral buffer spring 24, yieldably urges the oscillatory shaft 26 in the same direction. However, because of the considerable inertia of the oscillatory members, and particularly of the flywheel 4-2, a finite time will elapse before the oscillatory shaft 26 can follow the movement of the plate 16 of the solenoid 12.

Eventual rotation of the oscillatory shaft 26 and of the cam 44 brings a shoulder 44a (Figure 2) of the cam into contact With the resilient leaf 46a of the switch 46 and actuates the switch 46 to throw its contact blade 46b out of engagement with the fixed contact 46c and into engagement with the fixed contact 46d. This opens the circuit to the solenoid 12 and deenergizes the solenoid. Since the return spring is stiffer than the buffer spring 24, the deenergization of the solenoid 12 will allow the return spring 20 to rotate the movable plate 16 rapidly back to its starting position against the stop. This movement is imparted to the outer end of the buffer spring 24, and this yieldably urges the oscillatory shaft 26 back toward its starting position. the inertia of the system, a finite time will elapse before the oscillatory shaft 26 can follow the rotation of the plate 16 of the solenoid. When the shaft 26 does return 7 Again, however, because of to its initial position, the cam 44 disengages the leaf 46a of the switch 46, again actuating the switch 46 to the position indicated in Figure 3. This results in reenergizing the solenoid 12 and initiating a repetition of the cycle just described.

The oscillatory shaft thus oscillates back and forth at a frequency determined principally by the stiffness of the spring 24 and by the effective inertia of the system, the latter factor depending upon such variables as the mass and diameter of the fiy wheel 42 and the ratio between the gears 34 and 36. These variables may be changed to achieve any frequency of operation desired within wide limits.

As the oscillatory shaft 26 oscillates back and forth, the armature 46b of the switch 46 alternates between contact with the two fixed contacts 460 and 46d. When it is in engagement with the fixed contact 460 the lamps in the circuit 54 are illuminated, and when it is in engagement with the fixed contact 46d the lamps in the circuit 56 are illuminated. The lamps in the two circuits S4 and 56 are thus illuminated intermittently in alternation. The rotational position of the cam 44 on the oscillatory shaft 26 may be adjusted to move the shoulder 44a toward or away from the leaf 46a of the switch 46 in the position of rest. This makes it possible to cause one of the lamp circuits to operate more than half of the total cycle and the other a correspondingly lesser part of the cycle, if desired.

A study of the mechanism illustrated will reveal that each of the moving parts therein has a rotative movement about a fixed axis and that its mass is symmetrically disposed with respect to this axis. It will thus be understood that even violent translational accelerations will produce only a negligible efiect on these moving parts and will not affect their frequency of oscillation. The device is thus highly immune to the adverse eflects of vibration.

Because of the gear ratio between the spur 34 on the oscillatory shaft 26 and the pinion 36 on the countershaft 38, the countershaft 38 and flywheel 42 rotate at a substantially greater angular velocity than the shaft 26. This increases the effective inertia of the flywheel 42 and allows the use of a flywheel of relatively small mass to make possible a timing device which is quite compact and light in weight.

Since the time consumed by movement of the movable member 16 of the solenoid 12 is only a very small percentage of the period of oscillation of the oscillatory shaft 26, the operating voltage supplied to the device may vary over an exceptionally wide range without producing more than a very slight effect on the frequency of operation of the device.

Because the contacts 46b and 460 of the switch 46 are closed in the condition of rest, electrical current is supplied to the lamp circuit 54 even in the event of burning out of the solenoid 12 or jamming of the oscillating mechanism or other similar types of failures. Thus one set of lights on the airplane will be illuminated to maintain a degree of safety under practically all conditions.

It will therefore be appreciated that the present invention provides a timing device which is relatively simple in construction and operation and which is capable of maintaining its frequency of operation despite severe vibration and extreme voltage fluctuation. It will therefore be appreciated that the aforementioned and other desirable objectives have been achieved. However, it should be emphasized that the particular embodiment of the invention which is shown and described herein is intended as merely illustrative and not as restrictive of the invention. 1

I claim:

1. A timing device comprising an oscillatory member mounted for rotational oscillatory movement on an axis about which its mass is substantially symmetrically disposed, a solenoid having a movable member, a spring connected between the movable member of said solenoid and said oscillatory member whereby movement of said movable member upon the actuation of said solenoid yieldably urges said oscillatory member to rotate in a predetermined direction, and a switch arranged to be actuated by the rotational movement of said oscillatory member, said switch being connected to control the energization of said solenoid whereby movement of said oscillatory member in said one direction actuates said switch so as to deenergize said solenoid.

2. A timing device comprising an oscillatory member mounted for rotational oscillatory movement on an axis about which its mass is substantially symmetrically disposed, a rotary action solenoid having a movable member which is rotated in one direction by the energization of said solenoid, a return spring urging said movable member in the opposite direction, a spiral spring having one end connected to said oscillatory member and its other end connected to the movable member of said solenoid whereby energization of said solenoid yieldably urges said oscillatory member to rotate in said one direction, said spiral spring exerting a weaker force on the movable member of said solenoid than said return spring, and a switch arranged to be actuated by the rotational movement of said oscillatory member, said switch being connected to control the energization of said solenoid whereby movement of said oscillatory member in said one direction actuates said switch so as to deenergize said solenoid.

3. A timing device comprising an oscillatory member mounted for rotational oscillatory movement, a flywheel assembly mounted for rotational oscillatory movement on an axis about which its mass is substantially symmetrically arranged, driving elements interconnecting said flywheel assembly and said oscillatory member at such a drive ratio as to cause said flywheel assembly to rotate at an angular velocity in excess of that of said oscillatory member, a solenoid having a movable member, a return spring urging said movable member in the opposite direction, a spiral spring having one end connected to said oscillatory member and its other end connected to the movable member of said solenoid whereby energization of said solenoid yieldably urges said oscillatory member to rotate in said one direction, said spiral spring exerting a weaker force on the movable member of said solenoid than said return spring, and a switch arranged to be actuated by the rotational movement of said oscillatory member, said switch being connected to control the energization of said solenoid whereby movement of said oscillatory member in said one direction actuates said switch so as to deenergize said solenoid.

4. A timing device comprising an oscillatory member mounted for rotational oscillatory movement on an axis about which its mass is substantially symmetrically disposed, a rotary action solenoid having a movable member which is rotated in one direction by the energization of said solenoid, a spiral return spring connected at its inner end to the movable member of said solenoid and at its outer end to the frame of said device, a spiral buffer spring connected at its inner end to said oscillatory memher and at its outer end to the movable member of said solenoid whereby energization of said solenoid yieldably urges said oscillatory member to rotate in said one direction, said buffer spring exerting a weaker force on the movable member of said solenoid than said return spring, and a switch arranged to be actuated by the rotational movement of said oscillatory member, said switch being connected to control the energization of said solenoid whereby movement of said oscillatory member in said one direction actuates said switch so as to deenergize said solenoid.

5. An intermittent electrical control device comprising an oscillatory member mounted for rotational oscillatory movement on an axis about which its mass is substantially symmetrically disposed, a solenoid having a movable 5 member, a spring connected between the movable member of said solenoid and said oscillatory member whereby movement of said movable member upon the actuation of said solenoid yieldably urges said oscillatory member to rotate in a predetermined direction, a switch actuating member mounted on said oscillatory member for movement therewith, a first pair of switch contacts arranged to be actuated by said switch actuating member, said first pair of switch contacts being connected to cause the de-energization of said solenoid whereby movement of said oscillatory member in said one direction actuates said switch so as to deenergize said solenoid, a second pair of switch contacts adapted to be actuated by said switch actuating member, said second pair of switch contacts being adapted to control an external electrical circuit, and said switch actuating member being mounted on said oscillatory member for adjustment to various rotational positions to vary the times of actuation of said pairs of switch contacts.

References Cited in the file of this patent UNITED STATES PATENTS 1,659,850 Zorn Feb. 21, 1928 1,731,808 Barnes Oct. 15, 1929 2,205,909 Place June 25, 1940 

